1. Field
The present invention relates to a method and apparatus for performing electromagnetic tests on components in an enclosed chamber.
2. Background
Aircraft are occasionally struck by lightning when traveling near or through a thunderstorm. Because, until recently, most aircraft structure was aluminum, these strikes did little or no damage. With more aircraft structure being fabricated from composite material, the electromagnetic effects of lightning strikes have taken on greater significance. In particular, an electrical strike may cause arcing between different components in the aircraft. This type of arcing is undesirable because an arc may cause flammable vapors or liquids in the aircraft to ignite.
In designing an aircraft, the different designers and engineers take into account electromagnetic effects, such as lightning. For example, cables and equipment are protected from damaging surges or transients through techniques such as shielding, grounding, and the application of surge protection or suppression devices. As another example, fuel systems and other systems that carry flammable liquids or vapors are an area of concern because even a tiny spark or arc may be disastrous. Extreme precautions are taken to assure that currents caused by lightning strike cannot cause sparks in any portion of an aircraft's fuel system. All of the structural joints and fasteners are designed to prevent sparks as lightning current passes from one section to another section of the aircraft. Other components such as access doors, fuel filler caps, and vents are designed to withstand lightning. All of the fuel lines that carry fuel into the engines are verified to be protected against lightning. Similar design concerns are made with respect to other systems that carry flammable fluids or vapors.
In verifying these designs, tests are performed on the various components to ensure that simulated lightning strikes do not cause arcing. These same concerns are also present in other environments in which high voltages or large electrical currents may occur.
Currently, testing is performed in a number of different ways. Electrical arcing may be determined to have occurred using photographic paper in a darkened chamber or by the ignition of a flammable mixture that has been introduced into an enclosed chamber. When using the ignition method, the particular component is placed into a chamber and the component is connected to an electrical source. A flammable gas mixture is introduced into the chamber and the electrical source is activated to simulate an electromagnetic event, such as a lightning strike. Should an ignition event be observed, it is assumed that arcing of sufficient energy to initiate the ignition has occurred.
Large chambers are currently used to test the many different possible components that go into an aircraft. Further, the existing testing systems require the test setup to be dismantled and reassembled between tests. These types of testing systems are time consuming and expensive because of the time and amount of gas required for each test. The individual setups for each test require a great deal of time and effort between each test and most test programs involve many separate tests. Added up these multiple tests require a great deal of time to setup, disassemble, and reassemble. In addition, the large chamber volume requires additional gas mixture and the time required to fill the chamber multiple times.